The invention relates to a method for producing a control panel fascia, particularly for heating the cockpit of a vehicle, intended to have at least one rotary knob, comprising a mounting plate which defines a front face of the fascia and, for each knob, a tubular wall extending backwards from the mounting plate and meeting the latter along the edge of an approximately circular opening formed therein, the tubular wall having, in succession, in the axial direction, a first region adjacent to the opening and having approximately the same radius thereof, housing a head of the knob over at least part of the axial length thereof, and a second region of smaller radius than the head, meeting the first region at a shoulder, housing and guiding the rotation of a guide stalk of the knob, the head and the front face, near the opening, carrying marks and/or symbols which can be brought to face each other depending on the position into which the knob is turned, and which may be illuminated, through the material of the knob and the fascia, from a light source placed behind this fascia.
The term "radius" here denotes a distance with respect to an axis, which can vary in the circumferential direction when the element in question is not strictly circular. In this case, the inequalities mentioned for the radii of various elements need to be verified all around the axis.
The expression "front face" denotes that face of the mounting plate which faces towards the user of the control panel, and the terms "front" and "rear" refer to this convention. Note that in the case of a vehicle heating control panel, the front face generally faces the rear of the vehicle.
Forming the front face of the mounting plate with a film of transparent thermoplastic material which is inked by silkscreen printing to form colored marks and/or symbols and to make the rest of the surface opaque is known. The shoulder of the tubular wall, which is behind the head of the knob, must allow light from the light source through to illuminate at least one mark present on the head and intended to come to face various symbols depending on the position into which the knob is turned. By contrast, light must not pass around the head of the knob, between this head and the first region of the tubular wall.
To achieve this, it has been proposed that the tubular wall be made of transparent material, and that the silkscreen printed film be dished in such a way that it also covers part of the internal face of the tubular wall, as far as up behind the annular gap between the first region of this wall and the head. However, this has led to a deformation of the symbols and marks during the dishing operation, and to tearing and cracking of the film, leading to a high reject rate.